Project: Direct Operator Control Measurement

Overview

Problem

The original tractor control mechanisms relied heavily on sensors (primarily encoders and potentiometers) that directly measured the position of the mounted drive motors. When designing control loops for these systems, a number of drawbacks come to light:

1. The control loop is controlling the position of the motor rather than the position of the overall mechanical system. This becomes an issue when the tractor is being converted between manually and autonomously driven, and the pins connecting the motors to the drive systems are broken. If these pins are not replaced into identical positions, the system can no longer function properly. This opens the door for operator error.
2. Motors can spin continuously. If a continuous motor is attached to a limited sensor (such as a numbered turn potentiometer) and the control loop fails, the motor can break the sensor.

Solution

An alternative sensing mechanism is to attach new sensors directly to the mechanical controls of the tractor, rather than to the motor. This system solves the two problems above in the following manner:

1. The control loop will control the overall position of the tractor regardless of the position of the motor, allowing the system to compensate for and operator inconsistency in detaching and re-attaching systems.
2. The tractor components cannot move continuously, and as such cannot break the sensing systems if they are chosen and designed correctly.

Background Reading

• Arrow "Encoders vs Potentiometers: Which is Right for your Project?"
• Encoder
  • Electropeak "Rotary Encoder: How it Works and How to Use it with Arduino"
• Potentiometer
  • Electrical4U "Potentiometer: Definition, Types, and Working Principle"
• Cable Encoder
  • Encoder "Linear Cable Encoder Model LCE"
• Ingress Protection Ratings
  • DSM&T "IP Rating Chart"

Project 1: Steering Sensor Design

Mechanical

• Determine a few options for sensor types and monitoring locations on the steering system
• Choose one sensor and corresponding monitoring location
• Spec out sensor
  • IP65 or greater
  • Unable to be destroyed by natural movement of steering system
  • Does not interfere with operation of steering system or other systems
  • Preferably not some weird-ass communication protocol
• CAD relevant components of the steering system, sensor, and any mounting hardware required
• Purchase relevant sensor, hardware, etc.
• Manufacture any parts necessary
• Mount system

Electrical

• TODO

Software

• TODO

Project 1: Velocity Pedal Sensor Design

Mechanical

• Determine a few options for sensor types and monitoring locations on the steering system
• Choose one sensor and corresponding monitoring location
• Spec out sensor
  • IP65 or greater
  • Unable to be destroyed by natural movement of steering system
  • Does not interfere with operation of steering system or other systems
  • Preferably not some weird-ass communication protocol
• CAD relevant components of the steering system, sensor, and any mounting hardware required
• Purchase relevant sensor, hardware, etc.
• Manufacture any parts necessary
• Mount system

Electrical

• TODO

Software

• TODO